In-line modelling of dust in the convective scale NWP model AROME

Acknowledged as one of the leading international laboratory in matter of meteorological research, CNRM (http://www.umr-cnrm.fr/) is the main Météo-France lab in R&D. In partnership with CNRS, its main missions are to have a better understanding of the atmosphere, its interfaces (soil, vegetation, snow cover, ocean), the processes governing their interactions and the atmospheric models: weather forecasting, climate changes, seasonal forecasting, peaks of pollution, avalanche occurrences, floods, etc.

Context:

The simulation of the coupled evolution of atmospheric transport and aerosols/chemistry is one of the most challenging tasks in environmental modelling. It is well accepted that weather is a key element for air quality. It is also recognized that chemical species and aerosols can influence weather by changing the atmospheric radiation budget as well as cloud microphysics. However, until recently, aerosol feedbacks have been neglected in NWP systems. Because of a better understanding of underlying interaction mechanisms and a continuous increase in computer power, it is timely now to introduce progressively in-line aerosols and chemistry coupling within NWP systems. An additional attractiveness of the on-line approach is its possible benefit for meteorological data assimilation.

The AROME convective scale model (Seity et al. 2011, Brousseau et al. 2016) is operational at Météo-France since December 2008. AROME-France is the regional deterministic forecast model over France mainland, with at present a resolution of 1.3km, 90 vertical levels and a one-hour data assimilation cycle. Météo-France operates several other operational AROME-based configurations : a nowcasting system, several overseas and assistance systems, an ensemble prediction system. The description of aerosols and chemistry in these AROME configurations is based on climatologies.

Description of work:

Desert dust modules have been activated in AROME model by Kocha (2013) in order to provide predictions of dust events during the FENNEC measurement campaign (Chaboureau et al., 2016). Desert dusts emission processes are managed by the DEAD model (Grini et al., 2006). The transport, deposition and leaching processes are managed by the ORILAM log-normal aerosol scheme (Tulet et al., 2005). The validation of this configuration has been extended recently (Ambar and Mokhtari, 2017). The additional cost of dust modules represents currently a 50% increase in CPU.

The overall objective of the post-doc is to develop an AROME NWP configuration including in-line dust modelling for an operational perspective. Accurate operational forecasts of dust emission and transport are a societal demand worldwide as they pertain to many health and economic issues.

The first step will consist in the development of several AROME configurations with a variable level of complexity in the representation of dust interactions (with or without radiation interactions, with a reduced number of modes and/or moments, etc.). The feasibility of implementing an alternative version based on a sectional (bin) approach will be also considered.

In the second step, the use of MACC and MOCAGE operational forecasts as initial and lateral boundary conditions for AROME-Dust will be developed and evaluated. The feasibility of coupling to an ARPEGE configuration including in-line dust modelling will be studied.

In a third step, these configurations will be evaluated with observations from experimental campaigns (ChArMEx/ADRIMED or DACCIWA), giving the opportunity to validate not only optical depth, but also some other aspects such as size distribution, optical and micro-physical properties, radiative effects of dust aerosols. This work could be a contribution to an intercomparison of dust simulations with several models (ALADIN-NWP, ALADIN-Climat, MOCAGE, etc.).

Supervision team: The work will be conducted under the main supervision of François Bouyssel from CNRM in Toulouse.

Required qualifications: The candidates should have either a PhD or an engineer diploma in atmospheric, environmental sciences or computational fluid dynamics and should speak English fluently. Experience in mesoscale modelling or knowledge on aerosols/chemistry processes would represent considerable additional skills. Good programming skills (Fortran, Unix/linux shell scripts) are required.

Duration and salary: The successful applicant will be recruited for 12 months with a net monthly salary between 2600 and 3000 euros, commensurate with experience and qualifications. This includes social services and health insurance.

Contact for applications: Application should be done by e-mail to François Bouyssel (francois.bouyssel@meteo.fr) by sending a CV, a statement of research interests and the names of at least two referees including e-mail addresses and telephone numbers before 24 February 2017.